Circulation and suspended sediment transport in a coral reef lagoon: The south-west lagoon of New Caledonia

Ouillon, Sylvain; Douillet, Pascal; Lefèbvre, J.; Gendre, Romain Le; Jouon, Aymeric; Bonneton, Philippe; Fernandez, Jean-Michel; Chevillon, Christine; Magand, Olivier; Lefêvre, Jérôme; Hir, Pierre Le; Laganier, Richard; Dumas, Franck; Marchesiello, Patrick; Madani, A. Bel; Andréfouët, Serge; Panche, Jean-Yves; Fichez, Renaud

doi:10.1016/j.marpolbul.2010.06.023

Cited by 100 publications

(90 citation statements)

References 121 publications

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“…Specifically at Sugarloaf Key in the Lower Florida Keys, tides and associated tidal currents, storms, and upwelling events led to short-term increases in turbidity and in spectral particulate absorption, attenuation and scattering in the patch reef and seagrass sites. Tides and circulation dynamics in coastal waters can resuspend sediments and dissolved compounds changing the chemical composition of the water column when organic and inorganic materials trapped in the sediments are released [23][24][25][26][57][58][59].…”

Section: Discussionmentioning

confidence: 99%

Characterization of Available Light for Seagrass and Patch Reef Productivity in Sugarloaf Key, Lower Florida Keys

et al. 2016

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Light availability is an important factor driving primary productivity in benthic ecosystems, but in situ and remote sensing measurements of light quality are limited for coral reefs and seagrass beds. We evaluated the productivity responses of a patch reef and a seagrass site in the Lower Florida Keys to ambient light availability and spectral quality. In situ optical properties were characterized utilizing moored and water column bio-optical and hydrographic measurements. Net ecosystem productivity (NEP) was also estimated for these study sites using benthic productivity chambers. Our results show higher spectral light attenuation and absorption, and lower irradiance during low tide in the patch reef, tracking the influx of materials from shallower coastal areas. In contrast, the intrusion of clearer surface Atlantic Ocean water caused lower values of spectral attenuation and absorption, and higher irradiance in the patch reef during high tide. Storms during the studied period, with winds >10 m¨s´1, caused higher spectral attenuation values. A spatial gradient of NEP was observed, from high productivity in the shallow seagrass area, to lower productivity in deeper patch reefs. The highest daytime NEP was observed in the seagrass, with values of almost 0.4 g¨O 2¨m´2¨h´1 . Productivity at the patch reef area was lower in May than during October 2012 (mean = 0.137 and 0.177 g¨O 2¨m´2¨h´1 , respectively). Higher photosynthetic active radiation (PAR) levels measured above water and lower light attenuation in the red region of the visible spectrum (~666 to~699 nm) had a positive correlation with NEP. Our results indicate that changes in light availability and quality by suspended or resuspended particles limit benthic productivity in the Florida Keys.

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Section: Discussionmentioning

confidence: 99%

Characterization of Available Light for Seagrass and Patch Reef Productivity in Sugarloaf Key, Lower Florida Keys

et al. 2016

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“…Oligotrophic ocean water enters the lagoon from the south and is driven north by the trade winds and tidal forcing before exiting through several deep inlets in the intertidal barrier reef that forms the western boundary of the lagoon (Ouillon et al, 2010). Primary productivity is N limited throughout the year , giving N 2 -fixing microorganisms a competitive advantage over nondiazotrophic organisms.…”

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confidence: 99%

Contribution and pathways of diazotroph-derived nitrogen to zooplankton during the VAHINE mesocosm experiment in the oligotrophic New Caledonia lagoon

et al. 2016

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Abstract. In oligotrophic tropical and subtropical oceans, where strong stratification can limit the replenishment of surface nitrate, dinitrogen (N 2 ) fixation by diazotrophs can represent a significant source of nitrogen (N) for primary production. The VAHINE (VAriability of vertical and tropHIc transfer of fixed N 2 in the south-wEst Pacific) experiment was designed to examine the fate of diazotroph-derived nitrogen (DDN) in such ecosystems. In austral summer 2013, three large (∼ 50 m 3 ) in situ mesocosms were deployed for 23 days in the New Caledonia lagoon, an ecosystem that typifies the low-nutrient, low-chlorophyll environment, to stimulate diazotroph production. The zooplankton component of the study aimed to measure the incorporation of DDN into zooplankton biomass, and assess the role of direct diazotroph grazing by zooplankton as a DDN uptake pathway. Inside the mesocosms, the diatom-diazotroph association (DDA) het-1 predominated during days 5-15 while the unicellular diazotrophic cyanobacteria UCYN-C predominated during days 15-23. A Trichodesmium bloom was observed in the lagoon (outside the mesocosms) towards the end of the experiment. The zooplankton community was dominated by copepods (63 % of total abundance) for the duration of the experiment. Using two-source N isotope mixing models we estimated a mean ∼ 28 % contribution of DDN to zooplankton nitrogen biomass at the start of the experiment, indicating that the natural summer peak of N 2 fixation in the lagoon was already contributing significantly to the zooplankton. Stimulation of N 2 fixation in the mesocosms corresponded with a generally low-level enhancement of DDN contribution to zooplankton nitrogen biomass, but with a peak of ∼ 73 % in mesocosm 1 following the UCYN-C bloom. qPCR analysis targeting four of the common diazotroph groups present in the mesocosms (Trichodesmium, het-1, het-2, UCYN-C) demonstrated that all four were ingested by copepod grazers, and that their abundance in copepod stomachs generally corresponded with their in situ abundance. 15 N 2 labelled grazing experiments therefore provided evidence for direct ingestion and assimilation of UCYN-C-derived N by the zooplankton, but not for het-1 and Trichodesmium, supporting an important role of secondary pathways of DDN to the zooplankton for the latter groups, i.e. DDN contributions to the dissolved N pool and uptake by nondiazotrophs. This study appears to provide the first evidence of direct UCYN-C grazing by zooplankton, and indicates that UCYN-C-derived N contributesPublished by Copernicus Publications on behalf of the European Geosciences Union.

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“…Bathymetry in lagoon does not exceed 70 m. The effect of non-algae particles (mineral suspended solids-NAP) is negligible in this typical oligotrophic lagoon, except in small enclosed and shallow bays. Measured SPM concentration ranges from 0.2 mg¨L´1 off the barrier reef to 0.38 mg¨L´1 in the middle part of the lagoon (deep lagoon) to up to 2 mgL´1 in bays [46] (there are exceptional values of 6 mg¨L´1 in some laterite impacted bays during special events, such as cyclones or strong rains [29,31]). In this study, few match-ups are in bays, and it is difficult to get match-ups during rainy events because of clouds.…”

Section: Behavior Of the Algorithm In New Caledonian Watersmentioning

confidence: 99%

A Statistical Algorithm for Estimating Chlorophyll Concentration in the New Caledonian Lagoon

et al. 2016

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Spatial and temporal dynamics of phytoplankton biomass and water turbidity can provide crucial information about the function, health and vulnerability of lagoon ecosystems (coral reefs, sea grasses, etc.). A statistical algorithm is proposed to estimate chlorophyll-a concentration ([chl-a]) in optically complex waters of the New Caledonian lagoon from MODIS-derived "remote-sensing" reflectance (R rs ). The algorithm is developed via supervised learning on match-ups gathered from 2002 to 2010. The best performance is obtained by combining two models, selected according to the ratio of R rs in spectral bands centered on 488 and 555 nm: a log-linear model for low [chl-a] (AFLC) and a support vector machine (SVM) model or a classic model (OC3) for high [chl-a]. The log-linear model is developed based on SVM regression analysis. This approach outperforms the classical OC3 approach, especially in shallow waters, with a root mean squared error 30% lower. The proposed algorithm enables more accurate assessments of [chl-a] and its variability in this typical oligo-to meso-trophic tropical lagoon, from shallow coastal waters and nearby reefs to deeper waters and in the open ocean.

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Circulation and suspended sediment transport in a coral reef lagoon: The south-west lagoon of New Caledonia

Cited by 100 publications

References 121 publications

Characterization of Available Light for Seagrass and Patch Reef Productivity in Sugarloaf Key, Lower Florida Keys

Characterization of Available Light for Seagrass and Patch Reef Productivity in Sugarloaf Key, Lower Florida Keys

Contribution and pathways of diazotroph-derived nitrogen to zooplankton during the VAHINE mesocosm experiment in the oligotrophic New Caledonia lagoon

A Statistical Algorithm for Estimating Chlorophyll Concentration in the New Caledonian Lagoon

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